Spatial turnover in the global avifauna

Despite its wide implications for many ecological issues, the global pattern of spatial turnover in the occurrence of species has been little studied, unlike the global pattern of species richness. Here, using a database on the breeding distributions of birds, we present the first global maps of variation in spatial turnover for an entire taxonomic class, a pattern that has to date remained largely a matter of conjecture, based on theoretical expectations and extrapolation of inconsistent patterns from different biogeographic realms. We use these maps to test four predictions from niche theory as to the form that this variation should take, namely that turnover should increase with species richness, towards lower latitudes, and with the steepness of environmental gradients and that variation in turnover is determined principally by rare (restricted) species. Contrary to prediction, we show that turnover is high both in areas of extremely low and high species richness, does not increase strongly towards the tropics, and is related both to average environmental conditions and spatial variation in those conditions. These results are closely associated with a further important and novel finding, namely that global patterns of spatial turnover are driven principally by widespread species rather than the restricted ones. This complements recent demonstrations that spatial patterns of species richness are also driven principally by widespread species, and thus provides an important contribution towards a unified model of how terrestrial biodiversity varies both within and between the Earth's major land masses.

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Metabarcoding to establish freshwater indicators of environmental degradation in the Indo-Burmese biodiversity hotspot

ARPHA Conference Abstracts ◽

10.3897/aca.4.e65364 ◽

2021 ◽

Vol 4 ◽

Author(s):

Alfried Vogler ◽

Md. Mizanur Rahman ◽

Alfred Burian ◽

Thomas Creedy

Keyword(s):

Species Richness ◽

Ecological Status ◽

Biodiversity Hotspot ◽

Anthropogenic Pressures ◽

Status Assessment ◽

Baseline Information ◽

High Species Richness ◽

Threatened Habitats ◽

The Tropics ◽

Highland Streams

Biodiversity hotspots of the world are increasingly exposed to anthropogenic pressures and resulting ecosystem breakdowns. However, biotic surveys for ecological status assessment are rarely conducted in poorly characterised, yet highly diverse ecosystems in the tropics and subtropics. Here, we addressed the challenge of developing a monitoring system for the highland streams of the Indo-Burmese biodiversity hotspot in Bangladesh, using a meta-barcoding approach to investigate the impacts of growing anthropogenic pressures on poorly studied invertebrate communities. Species richness and beta diversity in the region were correlated with anthropogenic stressors that varied greatly between sampling sites. A partial-network approach allowed us to identify potential indicator species for either a good or poor ecological status. Overall, our results document high species richness and pronounced responses to disturbance in these unexplored, but threatened habitats. In combination with classical taxonomy approaches, metabarcoding can therefore serve as a valuable tool to rapidly generate lacking baseline information facilitating the conservation of vulnerable ecosystems.

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Richness and phylogenetic diversity are affected by space and time in the megadiverse Atlantic Forest of South America

10.7287/peerj.preprints.27450v1 ◽

2018 ◽

Author(s):

José Thales da Motta Portillo ◽

Fausto Erritto Barbo ◽

Josué Anderson Rêgo Azevedo ◽

Ricardo Jannini Sawaya

Keyword(s):

Species Richness ◽

South America ◽

Atlantic Forest ◽

Phylogenetic Diversity ◽

Latitudinal Gradient ◽

Environmental Gradients ◽

Negative Relationship ◽

Latitudinal Gradients ◽

Tropical Regions ◽

The Tropics

Understanding variation of species richness along latitudinal gradients, with more species toward the tropics, represents a challenge for ecologists. Species richness also varies according to the available area, with more species in larger regions, with area and latitude posited as major drivers of richness variations. However, species richness does not fully capture the evolutionary history behind those patterns. Phylogenetic diversity can provide insights on the role of time and evolutionary drivers of environmental gradients. We analyzed here the latitudinal gradient of endemic snakes from the Atlantic Forest of South America, a megadiverse and highly threatened portion of the Neotropics. We assessed the effect of area and average clade age on species richness and phylogenetic diversity, testing whether species richness and phylogenetic diversity increase with area availability and in lower latitudes. We found that area can predict species richness, but not phylogenetic diversity. Brazilian southeastern mountain ranges include larger patches of Atlantic Forest and the highest richness levels, but generally harboring snakes from relatively recent clades (neoendemics). There is a negative relationship between species richness and average clade age along the latitudinal gradient, with older clades found mainly in northern portions, increasing phylogenetic diversity at lower latitudes. Different dimensions of diversity, species richness and phylogenetic diversity, are thus affected in different ways by area and time for speciation in the Atlantic Forest, and this may be a trend in highly diverse tropical regions.

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Richness and phylogenetic diversity are affected by space and time in the megadiverse Atlantic Forest of South America

10.7287/peerj.preprints.27450 ◽

2018 ◽

Author(s):

José Thales da Motta Portillo ◽

Fausto Erritto Barbo ◽

Josué Anderson Rêgo Azevedo ◽

Ricardo Jannini Sawaya

Keyword(s):

Species Richness ◽

South America ◽

Atlantic Forest ◽

Phylogenetic Diversity ◽

Latitudinal Gradient ◽

Environmental Gradients ◽

Negative Relationship ◽

Latitudinal Gradients ◽

Tropical Regions ◽

The Tropics

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Lack of congruence between terrestrial and epiphytic lichen strata in boreal forests

The Lichenologist ◽

10.1017/s0024282920000407 ◽

2021 ◽

Vol 53 (1) ◽

pp. 149-158

Author(s):

Robert J. Smith ◽

Sarah Jovan ◽

Susan Will-Wolf

Keyword(s):

Species Richness ◽

Boreal Forests ◽

Environmental Gradients ◽

Ground Layer ◽

Global Changes ◽

Layer Versus ◽

Epiphytic Lichen ◽

Incremental Change ◽

Compositional Gradients ◽

Environmental Responses

AbstractLichens occupy diverse substrates across tremendous ranges of environmental variation. In boreal forests, lichen communities co-occur in ‘strata’ defined by terrestrial or arboreal substrates, but these strata may or may not be interchangeable as bioindicators. Do co-occurring lichen strata have similar community structures and environmental responses? Could one stratum serve as a proxy for the other? We assessed variation in species richness and community compositions between ground-layer versus epiphyte-layer lichen strata in boreal forests and peatlands of interior Alaska. Species richness was lower and more spatially structured in the ground layer than the epiphyte layer. Richness of strata was not correlated. The most compositionally unique ground-layer communities were species-poor but contained regionally rare species not common in other plots. Variation in community compositions (ordination scores) were not congruent between strata (Procrustes congruence < 0.16 on 0–1 scale); the largest departures from congruence occurred where ground layers were species-poor. The best predictors of ground-layer community compositions were hydrological and topographic, whereas epiphytes were most associated with macroclimate and tree abundances. We conclude that lichens on different substrates ‘move in different circles’: compositional gradients did not agree and the environmental gradients most important to each lichen stratum were not the same. The conditions which strongly influence one vegetation stratum may have little bearing upon another. As global changes modify habitats, an incremental change in environment may lead community trajectories to diverge among lichen strata.

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Biodiversity hanging by a thread: the importance of fungal litter-trapping systems in tropical rainforests

Biology Letters ◽

10.1098/rsbl.2011.1115 ◽

2011 ◽

Vol 8 (3) ◽

pp. 397-400 ◽

Cited By ~ 11

Author(s):

Jake L. Snaddon ◽

Edgar C. Turner ◽

Tom M. Fayle ◽

Chey V. Khen ◽

Paul Eggleton ◽

...

Keyword(s):

Species Richness ◽

Leaf Litter ◽

Plant Diversity ◽

Habitat Complexity ◽

Tropical Rainforests ◽

Dramatic Reduction ◽

Experimental Removal ◽

Crucial Component ◽

High Species Richness ◽

Vital Resource

The exceptionally high species richness of arthropods in tropical rainforests hinges on the complexity of the forest itself: that is, on features such as the high plant diversity, the layered nature of the canopy and the abundance and the diversity of epiphytes and litter. We here report on one important, but almost completely neglected, piece of this complex jigsaw—the intricate network of rhizomorph-forming fungi that ramify through the vegetation of the lower canopy and intercept falling leaf litter. We show that this litter-trapping network is abundant and intercepts substantial amounts of litter (257.3 kg ha −1 ): this exceeds the amount of material recorded in any other rainforest litter-trapping system. Experimental removal of this fungal network resulted in a dramatic reduction in both the abundance (decreased by 70.2 ± 4.1%) and morphospecies richness (decreased by 57.4 ± 5.1%) of arthropods. Since the lower canopy levels can contain the highest densities of arthropods, the proportion of the rainforest fauna dependent on the fungal networks is likely to be substantial. Fungal litter-trapping systems are therefore a crucial component of habitat complexity, providing a vital resource that contributes significantly to rainforest biodiversity.

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Evaluating the role of contracting and expanding rainforest in initiating cycles of speciation across the Isthmus of Panama

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2012.0706 ◽

2012 ◽

Vol 279 (1742) ◽

pp. 3520-3526 ◽

Cited By ~ 37

Author(s):

Brian Tilston Smith ◽

Amei Amei ◽

John Klicka

Keyword(s):

Bird Species ◽

Tropical Regions ◽

Isthmus Of Panama ◽

Species Pairs ◽

The Matrix ◽

High Species Richness ◽

The Rich ◽

The Tropics ◽

The Impact

Climatic and geological changes across time are presumed to have shaped the rich biodiversity of tropical regions. However, the impact climatic drying and subsequent tropical rainforest contraction had on speciation has been controversial because of inconsistent palaeoecological and genetic data. Despite the strong interest in examining the role of climatic change on speciation in the Neotropics there has been few comparative studies, particularly, those that include non-rainforest taxa. We used bird species that inhabit humid or dry habitats that dispersed across the Panamanian Isthmus to characterize temporal and spatial patterns of speciation across this barrier. Here, we show that these two assemblages of birds exhibit temporally different speciation time patterns that supports multiple cycles of speciation. Evidence for these cycles is further corroborated by the finding that both assemblages consist of ‘young’ and ‘old’ species, despite dry habitat species pairs being geographically more distant than pairs of humid habitat species. The matrix of humid and dry habitats in the tropics not only allows for the maintenance of high species richness, but additionally this study suggests that these environments may have promoted speciation. We conclude that differentially expanding and contracting distributions of dry and humid habitats was probably an important contributor to speciation in the tropics.

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Seasonality in a taxocoenosis of molluscs from soft bottoms in the Bay of Cádiz (southern Spain)

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315401004829 ◽

2001 ◽

Vol 81 (6) ◽

pp. 903-912 ◽

Cited By ~ 25

Author(s):

Jose L. Rueda ◽

Manuel Fernández-Casado ◽

Carmen Salas ◽

Serge Gofas

Keyword(s):

Species Richness ◽

Correspondence Analysis ◽

Dominant Species ◽

Southern Spain ◽

Soft Bottom ◽

Soft Bottoms ◽

High Species Richness ◽

Bay Of Cadiz ◽

Bay Of Cádiz ◽

Autumn And Winter

The macrofauna of molluscs associated with soft bottoms in the Bay of Cádiz (southern Spain) was studied monthly from February 1994 to January 1996. The number of species (63) is high for a soft bottom and is related to environmental characteristics (growth of macrophytes) and the biogeographical setting of the studied area. Corbula gibba (∼90%) was the dominant species in this taxocoenosis together with the gastropod Nassarius pygmaeus and the bivalves Pandora inaequivalvis, Parvicardium exiguum and Macoma melo. The most frequent species during the two years was also the bivalve Corbula gibba (100%) followed by the gastropods Nassarius pygmaeus, Tricolia tenuis, Rissoa membranacea and the bivalve Macoma melo. Total abundance of the taxocoenosis in both years reached higher values in spring. The dynamics of the ecological indices such as diversity or evenness, and the species richness showed a similar pattern in both years, with low values of diversity and evenness together with high species richness in spring and summer months and the reverse in autumn and winter. The qualitative correspondence analysis of monthly samples shows an ordination related to seasonality in both studied years, however the values of Jaccard's coefficient do not indicate significant boundaries among the monthly samples. The quantitative correspondence analysis shows an ordination and grouping of samples related to the biology of species, particularly with the recruitment of C. gibba, the dominant species. The existence of similar trends in the structure of the taxocoenoses over both years, and the seasonality highlighted by the qualitative correspondence analysis, seems to indicate a certain stability of the ecosystem.

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